The present embodiments relate to an adaptive x-ray filter for changing a local intensity of x-rays.
In examinations with the aid of x-rays, a patient and/or organs of the patient in a region to be examined may exhibit a very different absorption behavior with respect to the applied x-rays. For example, with thorax imaging, the attenuation in the mediastinum (i.e., in the region in front of the lungs) is very great due to the organs arranged there. In the region of the lungs, the attenuation is very low. To obtain a useful image and to protect the patient, the applied dose may be set depending on the region, so that no more x-rays than are needed are supplied. In other words, a greater dose is to be applied in regions with greater attenuation than in regions with less attenuation. In some applications, only part of the examined region is to be imaged with significant diagnostic quality (e.g., with little noise). The surrounding parts may be important for orientation but not for the actual diagnosis. These surrounding regions may be mapped with a lower dose in order to reduce the entire dose applied.
Filters are used in order to attenuate x-rays. A filter of this type is known, for example, from DE 44 22 780 A1. The filter has a housing with a controllable electrode matrix that generates an electric field. The electric field acts on a fluid connected to the electrode matrix, in which ions absorbing x-rays are present. The ions absorbing x-rays are freely moveable and roam around as a function of the applied field. With such a corresponding electric field embodiment, correspondingly more or fewer ions may be accumulated in the region of one or more electrodes to change the absorption behavior of the filter locally.
Electroactive polymers (EAP) that change form based on application of an electrical voltage are known from the prior art. One example of an electroactive polymer is a dielectric elastomer. A dielectric elastomer converts electrical energy directly into mechanical work. An actuator based on a dielectric elastomer may be constructed, for example, by coating an elastomer film on both sides with electrodes. An electric voltage may be applied to the elastomer film. The applied voltage compresses the elastomer film in the thickness direction, where the elastomer film extends laterally. With this process, the elastomer film may perform work and thus act as an actuator. If the voltage between the electrodes is removed again, the elastomer film reassumes an original form.